Non-ionic CT contrast solutions rapidly alter bovine cartilage and meniscus mechanics

Objective: To evaluate effects of a common CT contrast agent (iohexol) on the mechanical behaviors of cartilage and meniscus. Methods: Indentation responses of juvenile bovine cartilage and meniscus were monitored following exposure to undiluted contrast agent (100% CA), 50% CA/water, 50% CA/Phosphate Buffered Saline (PBS) or PBS alone, and during re-equilibration in PBS. The normalized peak force ((F-pk) over bar), effective osmotic strain (epsilon(osm)), and normalized effective contact modulus ((E-c) over bar) were calculated for every cycle, with time constants determined for both exposure and recovery via mono- or biexponential fits to (F-pk) over bar. Results: All cartilage CA groups exhibited long-term increases in (F-pk) over bar following exposure, although the hyperosmolal 100% CA and 50% CA/PBS groups showed an initial transient decrease. Meniscus presented opposing trends, with decreasin (F-pk) over bar for all CA groups. Re-equilibration in PBS for 1hr after exposure to 100% CA produced recovery to baseline (F-pk) over bar in cartilage but not in meniscus, and extended tests indicated that meniscus required similar to 2.5 h to recover halfway. (E-c) over bar increased with CA exposure time for cartilage but decreased for meniscus, suggesting an increased effective stiffness for cartilage and decreased stiffness for meniscus. Long-term changes to epsilon(osm) in both tissues were consistent with changes in (E-c) over bar. Conclusion: Exposure to iohexol solutions affected joint tissues differentially, with increased cartilage stiffness, likely relating to competing hyperosmotic and hypotonic interactions with tissue fixed charges, and decreased meniscus stiffness, likely dominated by hyperosmolarity. These altered tissue mechanics could allow non-physiological deformation during ambulatory weight-bearing, resulting in an increased risk of tissue or cell damage. (C) 2020 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.